Pathology-Designed Custom Molded Foot Orthoses

Transcription

1 Pathology-Designed Custom Molded Foot Orthoses Kevin B. Rosenbloom, CPed KEYWORDS Foot orthoses Custom orthoses Orthotic devices Pathology-designed orthoses Orthosis design Treating patients with custom foot orthoses for common pathologies is a rewarding experience when the proper steps are taken during foot casting and custom-orthosis prescription writing. This article describes successful methods for orthoses casting and prescription writing for custom-molded orthoses for Achilles tendonitis, pes planus, hallux limitus, plantar fasciitis/heel spurs, lateral ankle instability, metatarsalgia, and pes cavus. In addition, a summary of orthotic laboratory instructions for each pathology-designed orthosis is provided, which should be considered by orthotic laboratories. ACHILLES TENDONITIS When treating Achilles tendonitis with custom-molded foot orthotics, the most important function of the orthosis is to relieve tension on the Achilles tendon by plantar-flexing the foot and then reducing any internal or external rotation of the Achilles tendon by supporting the heel with corrective posting and custom contour inferior of the midtarsal joints. 1 Plantar flexion of the foot can be achieved with a simple heel lift in a shoe or by wearing shoes with elevated heels such as running shoes or clogs. It is important for patients to forgo wearing flat shoes and soft surfaces where the heel has a tendency to sink below the grade of the forefoot; walking barefoot should also be avoided. In a foot with normal mechanics, controlling eversion or inversion of the calcaneus is critical for prevention of rotational torsion of the Achilles. A deep heel cup with extrinsic varus or valgus posting will control any subtalar eversion or inversion while ambulating (Figs. 1 and 2). The full contact orthosis shell is important for full functionality of the rearfoot posting and controlling midtarsal joint articulation. Proper casting is also critical. While suspension casting with plaster or a similar material, one must load the midtarsal joints to a pronated position while keeping the subtalar joint neutral. 2,3 It is very important that the laboratory replicate the casted position with the positive model using minimal medial arch fill and no plaster build-up on the medial aspect of the Kevin Orthotics, Foot In Motion, rd Street, Santa Monica, CA 90405, USA address: [email protected] Clin Podiatr Med Surg 28 (2011) doi: /j.cpm podiatric.theclinics.com /11/$ see front matter Ó 2011 Elsevier Inc. All rights reserved.

2 172 Rosenbloom Fig. 1. Achilles tendonitis pathology-designed orthosis, medial posterior view of 16-mm heel cup, extrinsic post with 3-mm heel lift. Anterior view of custom molded polypropylene shell with vinyl top cover terminating proximal to the metatarsal heads. heel. A high-quality polypropylene shell material that is semirigid and selected according to the patient s weight for 5% to 10% give and rebound should be employed for optimal results in comfort and control. 4 A slim vinyl top cover keeps the custom-molded orthosis shell intimate with foot contour. The custom orthosis should terminate proximal to the metatarsal heads to position the forefoot below the elevation of the heel throughout the gait cycle (Fig. 3). Custom orthoses designed for Achilles tendonitis should be worn by the patient full-time after the break-in period and should then be worn for the life of the patient to prevent recurrence. For orthotic laboratory instructions, see Box 1. PES PLANUS Pes planus can be a difficult yet rewarding pathology to treat with orthoses. Fighting gravity, mechanical inefficiencies, and accommodating bony prominences in the foot is challenging for the foot and ankle specialist. Careful casting is critical for pes planus foot architecture. A foam impression may prove sufficient if the goal is merely to support and accommodate the present foot structure. However, custom orthosis correction is usually desirable in order to prevent degenerative mechanics and inefficient gait. Suspension casting is preferred. 3 Fig. 2. Achilles tendonitis pathology-designed orthosis, posterior view, with 4 rearfoot posting and 3-mm heel lift. extrinsic

3 Pathology-Designed Custom Foot Orthoses 173 Fig. 3. Achilles tendonitis pathology-designed orthosis, medial view, terminating proximal to the metatarsal heads. Polypropylene custom-molded shell, 4 extrinsic rearfoot posting, 3-mm heel lift. To position the foot for correct casting, a full understanding of the weight-bearing position is needed to determine how much deformity is present during ambulation. A subtalar neutral position with a fully pronated midtarsal joint captures a corrected foot position that is tolerable. 3 Bony prominences require button-out accommodations, especially the navicular and talus head. Button-out accommodations should be slightly greater than their respective size to allow for some orthosis shear and movement. The orthotic laboratory should be familiar with proper placement and sizing of button-out accommodations; however, the laboratory may require prominences to be marked accordingly on the negative cast. A forefoot varus wedge inferior to the metatarsal heads posted to the degree of forefoot varus is an effective method to prevent mid- and rear-foot compensation for the forefoot varus deformity. Attention to proper shoe gear that allows enough room for the forefoot wedge is required. Medial flange and lateral clip, coupled with proper shoe gear, minimizes foot eversion, abduction, and lateral sliding off the orthosis. Vinyl top covers over a shell constructed of polypropylene will control and support the foot with comfort. Shell reinforcement is usually necessary in the form of an ethyl vinyl acetate (EVA) arch fill to provide longlasting support. A very deep heel cup and extrinsic posting to correct subtalar eversion creates a solid foundation for the pes planus foot (Figs. 4 6). Pes planus designed Box 1 Achilles tendonitis: custom foot orthosis laboratory instructions Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Minimal Shell Material: Polypropylene per weight Heel Cup Depth: 16 mm (deep) Shell Width: Standard (medial edge bisecting the sesamoids, lateral edge bisecting the fifth metatarsal head) Rearfoot Posting: Extrinsic crepe posted to correct reducible varus or valgus heel position with 3-mm heel lift bilateral Extension: None Top Cover: Vinyl Bottom Cover: None

4 174 Rosenbloom Fig. 4. Pes planus designed orthosis, inferior view, forefoot varus posting inferior of the metatarsal heads. Fig. 5. Pes planus designed orthosis, blue EVA arch reinforcement, varus rearfoot posting, medial flange, lateral clip to prevent lateral slipping. Fig. 6. Foot with pes planus designed orthosis, forefoot varus wedge under the metatarsal heads, blue EVA arch reinforcement, medial flanged polypropylene custom-molded shell, varus extrinsic heel post and deep heel cup.

5 Pathology-Designed Custom Foot Orthoses 175 orthoses should be broken in accordingly and should be worn for the lifetime of the patient. For orthotic laboratory instructions, see Box 2. HALLUX LIMITUS Treatment of functional hallux limitus with custom-molded foot orthoses is rewarding, and positive mechanical results are present nearly immediately when orthosis prescriptions are written correctly and when the orthotic is correctly dispensed. The primary function of the orthosis is to increase range of motion of the first metatarsal phalangeal joint by preventing jamming moments of the first metatarsal phalangeal joint. Underlying mechanical pathology of overpronating midtarsal and subtalar joints is often present with functional hallux limitus. The goal of orthotic treatment is to correct hind- and mid-foot mechanics while enhancing dorsiflexion of the hallux with forefoot modifications. 5,6 Suspension casting while the subtalar joint is neutral and the midtarsal joint is fully pronated is crucial. Standard laboratory modification of the positive model is preferred: 3 mm of allowance for medial arch pronation and fat pad expansion. A custom-molded polypropylene shell is desirable for semirigid control along with rearfoot posting to correct calcaneus eversion or inversion. An extension that incorporates a functional modification to promote dorsiflexion of the hallux is critical to achieve desirable first metatarsal phalangeal joint range of motion. A dynamic wedge that elevates the second through fifth metatarsal heads at least 1.5 to 3 mm relative to the first metatarsal head allows the first metatarsal to plantar-flex, thus enhancing hallux dorsiflexion. A 1.5- to 3-mm elevation under the hallux further promotes hallux dorsiflexion (Fig. 7). This modification is essentially a balancing of the first metatarsal head and elevation of the distal hallux (Figs. 8 and 9). Vinyl top covers allow intimate control of the mid- and rearfoot and allow the dynamic wedge to function without the extra bulk of padding in the forefoot. Orthoses for hallux limitus require a break-in period, and should be worn for the lifetime of the patient to ensure proper mechanics and prevent degenerating stress on the first metatarsal phalangeal joint. For orthotic laboratory instructions, see Box 3. Box 2 Pes planus: custom foot orthosis laboratory instructions Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Standard Shell Material: Polypropylene per weight Shell Arch Fill: EVA Heel Cup Depth: 20 mm (very deep) Shell Width: Wide (medial edge medial to tibial sesamoid, lateral edge lateral to fifth metatarsal head) with medial flange and button out accommodations for bony prominences Rearfoot Posting: Extrinsic crepe posted to reduce varus heel position Forefoot Posting: Extrinsic crepe wedge to stabilize and accommodate forefoot varus position Extension: 3-mm cushion to toes Top Cover and Padding: Vinyl top cover and moderate padding Bottom Cover: Suede or similar

6 176 Rosenbloom Fig. 7. Hallux limitus designed orthosis, without top cover, revealing dynamic wedge extension. Fig. 8. Hallux limitus designed orthosis, without top cover, showing dynamic wedge extension assisting dorsiflexion of the hallux.

7 Pathology-Designed Custom Foot Orthoses 177 Fig. 9. Hallux limitus designed orthosis, without top cover, showing dynamic wedge extension assisting dorsiflexion of the hallux. HALLUX RIGIDUS Hallux rigidus can be a challenging pathology to treat, given the compliance of shoe gear that is required by the patient. The goal of custom-molded foot orthoses is to restrict all motion and moments in the first metatarsal phalangeal joint by creating a splinting type of modification across the joint on the plantar aspect to withstand and transfer dorsiflexion moments to the orthosis shell or shoe gear. These types of splints or modifications are commonly called Morton extensions. 7 Proper suspension casting is critical for distribution of pressure and overall comfort. Neutral subtalar joint positioning and fully pronated midtarsal joint positioning is ideal during suspension casting. A polypropylene shell with rigid Morton extension is the best method to prevent movements in the pathologic joint (Fig. 11). This orthosis modification is an extension of the orthosis shell made from polypropylene, which extends from the heel distal to the first metatarsal phalangeal joint. Complications of fitting shoe gear with fully rigid devices are often present with rigid Morton extensions. Conversations with the patient to educate him or her on shoe-gear selection and expectations are paramount for successful outcomes with modifications of rigid Morton extensions. Because of the limited shoe-gear selection and fitting issues with rigid Morton Box 3 Hallux limitus: custom foot orthosis laboratory instructions Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Standard Shell Material: Polypropylene per weight Shell Arch Fill: None Heel Cup Depth: 10 mm (standard) Shell Width: Standard (medial edge bisecting the sesamoids, lateral edge bisecting the fifth metatarsal head) Rearfoot Posting: Extrinsic crepe posted to correct reducible varus or valgus heel position Extension: Dynamic wedge extension (to promote hallux dorsiflexion) to toes Top Cover: Vinyl Bottom Cover: Suede or similar

8 178 Rosenbloom extensions, very often semiflexible Morton extensions are prescribed to provide some relief to the rigid first metatarsal phalangeal joint (Fig. 10). These semiflexible extensions absorb some dorsiflexion moments of the first metatarsal phalangeal joint, and satisfactory results are achieved in mild to moderate cases. The semiflexible extension should be crafted from a firm cushioning material such as EVA or crepe and extend from the distal shell, proximal to the metatarsal heads, extending distally past the first metatarsal phalangeal joint. Laterally, the rigid or semiflexible Morton extension should terminate at the first interspace. With a rigid or semiflexible Morton extension, a 1.5- to 3-mm cushioned top cover is desirable for comfort and acceptance of the topographic features of the Morton extension. Patients with hallux rigidus should use a proper break-in period to become accustomed to their custom-molded orthoses, and the orthoses should be worn for the lifetime of the patient. For orthotic laboratory instructions, see Box 4. PLANTAR FASCIITIS AND HEEL SPURS Treating plantar fasciitis and heel spurs with custom-molded foot orthoses is effective when accomplished through a modification used to offload the inflamed tissue and a mechanical correction to reduce tension on the plantar fascia. 8 During suspension casting, it is critical to load the mid-tarsal joint to maximum pronation while keeping the subtalar joint neutral. It is also critical to take note of the swelling in the affected heel(s) and palpate for extra tissue mass on the plantar surface of the heel. If Fig. 10. Hallux rigidus pathology designed orthoses, rigid shell incorporating Morton extension.

9 Pathology-Designed Custom Foot Orthoses 179 Fig. 11. Hallux rigidus pathology designed orthoses, crepe flexible Morton extension. inflammation or asymmetric plantar mass is present at any location along the plantar surface of the heel, it is critical to write on the orthotic prescription that extra heel tissue expansion or accommodation is required for the pathologic heel. Modifications of the heel cup should accommodate for the inflamed area and for the spurring of the Box 4 Hallux rigidus: custom foot orthosis laboratory instructions Orthotic Type: Rigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Minimum Shell Material: Polypropylene per weight Shell Arch Fill: None Heel Cup Depth: 10 mm (standard) Shell Width: Standard (medial edge bisecting the sesamoids, lateral edge bisecting the fifth metatarsal head) Rearfoot Posting: Extrinsic crepe posted to correct reducible varus or valgus heel position Extension: Morton extension, rigid or semiflexible Top Cover: Cushioned Bottom Cover: Suede or similar

10 180 Rosenbloom Fig. 12. Heel spur pathology designed orthosis, uncovered custom-molded orthosis with horseshoe pad. calcaneus by offloading that area with a horseshoe-shaped pad (Fig. 12). The horseshoe-shaped pad should consist of a material that is firm yet cushioning. If spurs are not present, a heel cushion is recommended to provide extra comfort and heel elevation (Fig. 13). Three-millimeter cushion top covers provide sufficient cushion and comfort. An extrinsic post that corrects subtalar eversion or inversion by posting to the reducible position is also desirable to reduce rotational tension on the plantar fascia and underlying biomechanical pathology. A 3-mm heel lift bilateral, regardless of unilateral spurring and heel pain, helps reduce overall length of the plantar fascia. Deep heel cups help control calcaneus eversion and inversion; in addition they help contain excessive fat-pad expansion during weight bearing. Patients should follow a structured break-in period and continue to wear functional orthoses during rigorous activities for the duration of their lifetime to prevent reoccurrence. For orthotic laboratory instructions, see Box 5. LATERAL ANKLE INSTABILITY Treating lateral ankle instability with custom-molded orthoses is a challenge; one must fight a tendency toward lateral rolling and ankle sprains while making a comfortable, tolerable device First and foremost, a cast that positions the subtalar joint in

11 Pathology-Designed Custom Foot Orthoses 181 Fig. 13. Plantar fasciitis designed orthosis, uncovered custom-molded orthosis with heel cushion. Box 5 Plantar fasciitis and heel spurs: custom foot orthosis specifications Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Standard Shell Material: Polypropylene per weight Shell Arch Fill: None Heel Cup Depth: 16 mm (deep) Shell Width: Standard (medial edge bisecting the sesamoids, lateral edge bisecting the fifth metatarsal head) Rearfoot Posting: Extrinsic crepe posted to correct reducible varus or valgus heel position Extension: Thin cushion to toes Top Cover and Padding: Cushion to toes with horseshoe pad or heel cushion Bottom Cover: Suede or similar with 3 mm heel lift bilateral

12 182 Rosenbloom neutral while pronating the midtarsal joints is critical for achieving comfort and control. Then, standard fat pad expansion of 3 mm around the heel and 3-mm lowering of the arch are advisable in the cast. When patients present with high-arch, non-weight bearing that flattens to a pes planus position during weight bearing, maximum arch fill in the cast is desirable to lower the medial arch so as to prevent medial ground reaction force while wearing the orthosis. Any medial ground reaction force should be avoided. Modifications for lateral ankle instability orthoses should have an oblique valgus post that reduces the tension on the posterior talofibular ligament and calcaneofibular ligament (Fig. 14). Three degrees of valgus posting is ideal for patients whose calcaneus is aligned under the leg. A higher degree of correction may be needed for pes cavus foot types in the rearfoot as well as valgus posting in the forefoot. A cuboid pad should be added for the reduction of anterior talofibular ligament tension (Fig. 15). A cushioned extension to the toes is desirable for comfort. Lateral ankle instability designed orthoses should be worn by the patient for their lifetime and especially during intense activity. For orthotic laboratory instructions, see Box 6. METATARSALGIA Treating metatarsalgia with custom-molded foot orthoses is rewarding in most cases because the patient will experience a wow moment. Upon dispensing carefully crafted devices that offload pressure from the metatarsal heads during the propulsion phases of gait, significant relief is often experienced. First and foremost, a suspension cast that positions the subtalar joint in neutral while pronating the midtarsal joints is critical for achieving a contour of the arch that is in a functional position for propulsion as a rigid lever. 2 Minimal lowering of the arch in the cast is desirable to ensure close contact of the orthosis and arch during gait. Close contact of the arch will allow pressure to transfer from the metatarsal heads to the proximal osseous structures. The extension of the orthosis should offload the affected metatarsal heads when the patient describes pain in the precise location of 1 or 2 metatarsal heads. If general pain in the ball of the foot is the chief compliant and the patient has a Morton foot, a foot cookie modification in the extension is helpful in transferring propulsion moments to the first and fifth metatarsal heads while offloading the second, third, and forth metatarsal heads (Fig. 16). A metatarsal pad that is sized appropriately for the foot is also helpful for more severe cases that require more metatarsal shaft elevation, to attempt to offload the affected metatarsal Fig. 14. Lateral ankle instability pathology designed custom-molded orthosis, extrinsic valgus posting, lateral clip (left foot posterior view).

13 Pathology-Designed Custom Foot Orthoses 183 Fig. 15. Lateral ankle instability pathology designed orthosis, uncovered, blue cuboid pad, lateral clip, extrinsic oblique rearfoot post. head. 12,13 A small pad no larger than 3 mm in thickness is usually satisfactory. Mechanically the rearfoot should not be overlooked. Internal rotation of the metatarsal heads in the pronating foot can often cause an improper tracking of the lesser metatarsal phalangeal joints. This improper joint articulation can cause metatarsalgia, and attention to correct even the slightest pronation movement should be attempted with varus posting of the rearfoot. A 1.5-mm cushion top cover will allow full functionality of balance pads and foot cookie and metatarsal pad modifications, while providing comfort and cushioning. The designed orthosis should be worn by the patient for his or her lifetime to prevent recurring symptoms. For orthotic laboratory instructions, see Box 7. PES CAVUS The pes cavus foot is a demanding foot type to treat with custom-molded foot orthoses. Several mechanical pathologies proximal to the foot result from rigid foot architecture. Identifying the specific structure of the cavus foot can be a challenge. Plantar-flexed first rays are most common, causing the rearfoot to invert, resulting Box 6 Lateral ankle instability: custom foot orthosis laboratory instructions Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Standard Shell Material: Polypropylene per weight Shell Arch Fill: None Heel Cup Depth: 10 mm Shell Width: Wide (medial edge medial to tibial sesamoid, lateral edge lateral to fifth metatarsal head) with lateral clip Rearfoot Posting: Extrinsic crepe oblique valgus post Extension: 3 mm cushion to toes Top Cover and Padding: Vinyl, cuboid pad Bottom Cover: Suede or similar

14 184 Rosenbloom Fig. 16. Metatarsalgia pathology designed orthosis, uncovered, with foot cookie modification and metatarsal pad. in a foot that is unstable and at risk. To treat these foot types, a suspended cast is not as crucial due to the inflexibility of the foot. Foam box impression casting usually works as well as suspension slipper casting. 3,14 A loaded midtarsal joint that is fully pronated, and a neutral subtalar joint are preferred during casting and impression taking. If it presents, a plantar flexed first ray should be captured during the impression technique. The positive cast modification at the laboratory should contain minimal to no medial arch lowering, and standard fat pad expansion in the heel. A forefoot to rearfoot balancing is desired in the positive cast. The orthosis should have a rearfoot extrinsic post at neutral to valgus degree, depending on the angle of calcaneal varus. Forefoot balancing is also important to elevate the lesser metatarsal heads, allowing the first metatarsal head to drop. The trick of balancing the cavus foot with orthoses is to clinically observe the reduction of calcaneus varus obtainable and the severity of the plantar flexed first ray. Balancing by coupling moderate rearfoot post in the range of 2 to 4 valgus with a forefoot post of 2 to 4 valgus is usually effective. This balancing should also be coupled with a first metatarsal head balancing if there is a true plantar flexed first-ray deformity (Fig. 17). Not all cavus foot types have plantar flexed first rays; some have a forefoot Box 7 Metatarsalgia: custom foot orthosis laboratory instructions Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Minimal fill in medial arch Shell Material: Polypropylene per weight Shell Arch Fill: None Heel Cup Depth: 10 mm Shell Width: Standard (medial edge bisecting the sesamoids, lateral edge bisecting the fifth metatarsal head) Extension: Foot cookie modification (balance second, third, and forth metatarsal heads) Top Cover and Padding: Cushion top cover and metatarsal pads under affected metatarsals Bottom Cover: Suede or similar

15 Pathology-Designed Custom Foot Orthoses 185 Fig. 17. Pes cavus pathology designed orthosis, Coleman modification (valgus forefoot wedge with first metatarsal head cut-out filled in) (inferior view). perpendicular to the rearfoot or even a forefoot varus. 15 For the latter foot architectures, a cushioned, full-contact semirigid orthosis should be employed. Cavus foot patients should take care in breaking in orthoses and wear them for their lifetime in order to ensure a mechanically stable gait. For orthotic laboratory instructions, see Box 8. ORTHOTIC BREAK-IN With all custom-molded foot orthoses, a break-in schedule should be followed by the patient before wearing full time. Patient instructions with a preferred break-in schedule is as follows (but should be adjusted to consider patient age and health, and orthosis history; Box 9). PATIENT EDUCATION AND FOLLOW-UP It is important to educate patients in accommodating custom foot orthoses with properly fitting shoe gear for functionality and comfort. Custom-molded foot orthoses should never be forced into shoes, and they should sit flat and level within the shoe. Custom-molded foot orthoses should be checked annually for posting, top cover, Box 8 Pes cavus: custom foot orthosis laboratory instructions Orthotic Type: Semirigid functional Cast Balancing: Forefoot perpendicular to rearfoot Plaster Cast Fill: Minimal to none Shell Material: Polypropylene per weight Shell Arch Fill: None Heel Cup Depth: 10 mm Shell Width: Standard (medial edge bisecting the sesamoids, lateral edge bisecting the fifth metatarsal head) Rearfoot Posting: Extrinsic crepe valgus posting Extension: Coleman modification (valgus forefoot wedge posted to specific degree and first metatarsal head cut out with cushion fill-in) Top Cover: Vinyl Bottom Cover: None

16 186 Rosenbloom Box 9 Custom foot orthotic break-in period instructions (provide to patient when dispensing orthoses) It usually takes 10 days to become accustomed to your orthotics Follow the daily schedule for proper break-in: First day: Wear no longer than 1 hour Second day: Wear no longer than 2 hours Third day: DO NOT wear orthotics; take a break Fourth day: Wear no longer than 3 hours Fifth day: Wear no longer than 5 hours Sixth day: DO NOT wear orthotics; take a break Seventh day: Wear no longer than 7 hours Eighth day: Wear no longer than 9 hours Ninth day: DO NOT wear orthotics; take a break Tenth day: Wear up to 10 hours Eleventh day: Wear all day long! Do not wear orthotics for athletic activity during break-in period. Wait until after the 10th day before doing any intense activity like running or playing sports. If you experience any joint pain while wearing your orthotics, stop wearing your orthotics and contact the office. Your orthotics are custom made for you and your needs. They may require you to follow alternative instructions from your doctor. and shell breakdown. Orthoses should be replaced or repaired if posting or shells have lost their shape or if the top cover has become worn. SUMMARY These methods for foot casting and custom-orthosis prescription writing will provide positive outcomes for their intended pathology. Establishing a relationship with an orthotic laboratory that provides quality custom orthoses and quality service through communication will allow patients to receive the highest quality care and best possible outcome. REFERENCES 1. Donoghue OA, Harrison AJ, Laxton P, et al. Orthotic control of rear foot and lower limb motion during running in participants with chronic Achilles tendon injury. Sports Biomech 2008;7(2): Lee WE. Podiatric biomechanics: a historical appraisal and discussion of the root model as a clinical system of approach in the present context of theoretical uncertainty. Clin Podiatr Med Surg 2001;18(4): Losito JM. Impression casting techniques. In: Valmassy RL, editor. Clinical biomechanics of the lower extremities. St Louis (MO): Mosby; p Olson WR. Orthotic materials. In: Valmassy RL, editor. Clinical biomechanics of the lower extremities. St Louis (MO): Mosby; p

17 Pathology-Designed Custom Foot Orthoses Scherer PR, Sanders J, Eldredge D, et al. Effect of functional foot orthoses on first metatarsophalangeal joint dorsiflexion in stance and gait. J Am Podiatr Med Assoc 2006;96(6): Hetherington VJ, Johnson RE, Albritton JS. Necessary dorsiflexion of the first metatarsophalangeal joint during gait. J Foot Surg 1990;29: Jones JL. Prescription writing for functional and accommodative foot orthoses. In: Valmassy RL, editor. Clinical biomechanics of the lower extremities. St Louis (MO): Mosby; p Cheung JT, Zhang M, An KN, et al. Effect of Achilles tendon loading on plantar fascia tension in the standing foot. Clin Biomech (Bristol, Avon) 2006;21(2): Hertel J. Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. J Athl Train 2002;37: Orteza LC, Vogelbach WD, Denegar CR. The effect of molded and unmolded orthotics on balance and pain while jogging following inversion ankle sprain. J Athl Train 1992;27: Richie DH. Effects of foot orthoses on patients with chronic ankle instability. J Am Podiatr Med Assoc 2007;97: Chang AH, Abu-Faraj ZU, Harris GF, et al. Multistep measurement of plantar pressure alterations using metatarsal pads. Foot Ankle Int 1994;15: Hsi WL, Kang JH, Lee X. Optimum position of metatarsal pad in metatarsalgia for pressure relief. Am J Phys Med Rehabil 2005;84: Marzano R. Fabricating shoe modifications. In: Janisse D, editor. Introduction to pedorthics. Columbia (MD): Pedorthic Footwear Association; p Burns J, Crosbie J, Hunt A, et al. The effect of pes cavus on foot pain and plantar pressure. Clin Biomech 2005;20(9):